Lot of HVAC Videos at bottom of this page!Free Load-Calc
This Free online calc will help you determine equipment sizing & point-out
areas that need efficiency retro-work - Once you calculate the page it
saves the inputs for up to 24 minutes or, until you change inputs or close
your browser. You can easily reduce infiltration rates
yourself, therefore, I’d use 0.4 ACH (Air Changes per Hour) be sure to add the
(Air Changes per Hour) CFM into the ‘Fresh Air Recommended ‘line-slot, or
it won’t figure the Infiltration & fresh air Btuh.

You can experiment with changing the design
temperatures in both heat & cooling,
(or start-over showing the New Retro-R-Values) also to see whether the
equipment exceeds, at those particular temperatures & new retro
conditions, (exceeds) the Btuh calculation load numbers, 'in each' of the 3
cooling categories; Total Btuh, Sensible Btuh & Latent Btuh.

You're
going to gasp at what I suggest - however it will greatly improve a
3-Ton Return Air filtering situation, & blower
efficiency.
A filter grille, with a clean low resistant filter in accordance with
Manual D, should stay within 300-fpm velocity.
To achieve 300-fpm air flow velocity it will need 600-sq.ins., / by 144
or
4.1666-sq.ft of free air area. Therefore, 300-fpm * 4.1666-sq.ins. =
1250-cfm, that's 416.66-cfm per ton of cooling.Hart & Cooley engineering data shows a 36X24 Return air
filter grille with an Ak of 4.09-sf for 1227-cfm or, 3-ton of airflow
at 300-fpm velocity through the filter. 1227-CFM / 300-fpm is 4.09-Ak sf.

That
always
calls
for increased sizing for more Efficient Filtering & Return Airflow
Efficiency. You will never get too much RA filter area, the more the
better,
because as the filter loads the velocity will go above 500-fpm velocity
where the filter begins to allow too much debris blow-by.

Filter box
depth
sizing:
Having a large filter/grille area is of little value if there is
insufficient filter box depth, so that the RA duct is way too close to
the filter/grille.
Therefore, the depth of the filter/grille box &, when room permits,
"being funnel shaped" to
the
14” duct collar, is also important to efficient unrestricted airflow.

Figuring
650-CFM each Return Air duct run, that's 608-FPM Velocity. A 16"
return duct flowing 650-CFM would produce 466-fpm velocity.
Figure two 14” duct runs, if jammed too close to the filter, each duct
collar opening would only be 154-sq.ins., which explains why the filter
box depth is critically important to an unimpeded return airflow.Filter
mfg'ers ought to be required to list the sq.ft., free-air-area of their
new filters!So, what is the
free-air-area of the filter you are using?CFM / fpm velocity = sq.ft. area.-
Udarrell - Darrell

"What
Percent of
its
Designed EER, SEER, and (BTUH, BTUhr, BTU/hr,) is your Air Conditioner
delivering?"

keoffs are NOT blocked by the coil. In all cases, refer to the
manufacturers’
data for static pressure losses to ensure the total system static
pressure does
not exceed 0.5” WC.Rules
of
Thumb for Duct Systems - Hart&CooleyDESIGN
AND INSTALLATION OF RESIDENTIAL FLEXIBLE DUCTWORK SYSTEMShttp://www.dca.stae.ga.us/development/constructioncodes/publications/1ONE.pdfLook
at the ducting, if it is not to code; make hard copies of this code
& give it to whoever does the ducting work
Make sure they redo it right!Never
have flex duct interiors commercially cleaned, I just viewed Home
Inspection photos showing the interior damaged & insulation
plugging the duct.Home Inspectors warn people because the duct
cleaner's tell them it won't damage the ducts. Inspector's should
look into the boot areas for clues of problems...=============================================================Rules
of Thumb for Duct Systems - Hart&Cooley

Identifying
your registers/diffusers & their (Ak) (sf) sq.ft. area,
so you can
multiply the FPM Velocity times the Ak 'sf' area to get the (CFM) Cubic
Feet per
Minute airflow from that register.

http://www.americanmetalproducts.com/lima/product_catalogs.htmlClick on the
categories to see the diffusers & Return-Air Grilles then find them
on your downloaded pdf's engineering data.
Hart & Cooley: http://www.hartandcooley.com/grd/HC-100/residential/baseboard_registers/462.htm
Do a lot of Hart & Cooley engineering data searches, look at the
registers & the Ak sq.ft. data to figure supply & return air
grille & register's - delivered CFM.LOW
AIRFLOW <Click - this will help to open your eyes!=============================================================WARNING:on units
with a Thermostatic Expansion Valve (TXV), you cannot use the
suction pressure to check the charge; many appear to be doing this;
it
tells you nothing. Only after you have verified that all the coils are
clean & the
airflow is right-on, can you begin to check the system's charge using
Subcooling method with a Superheat check. Always check
the actual airflow
CFMbefore
checking the charge, get it Right!

* There
is a TXV system that has very low airflow, actually less than 200-cfm
per-ton of cooling, they're
only checking the suction pressure & saying the charge &
everything is okay! * That system has a TXV & shows; 98-F
condenser saturation temp & 97-F liquid line temp near E-Coil, a mere 1-F Subcooling, it's
undercharged even with a mere 200-cfm per-ton cooling load!
Unbelievable, but it's happening out there... Use my Superheat
Subcooling Charging page!Below
is an outstanding PDF
"Basic AC Overview - "Specifications
vs. Reality"
by John Proctor, P.E., Proctor Engineering Group, LTD: HVAC TECH
PERFORMANCE RATINGS"AC
Specs vs Reality" PDF - May not load?- It's
Worth Your Time

It’s important to
understand that "equipment ratings are
only the
potential efficiency of that component of the system under perfect
conditions." Over half of the system’s efficiency depends on the duct
system and the field-installation.

Optimizing
the
Evaporator
Heat Load at 75-F Room Temp will Optimize the Condenser BTUH Heat Load
Output, Check
your A/C-
Chart below Especially
if your system is oversized or there are a lot of low AC load days use
an Adjustable Differential Room TSTAT.TH
Differential:Differentialis defined as
the difference between the cut-in and cut-out
points as

measured at the thermostat
under specified operating conditions. For example, if the thermostat
turns

the
COOLING EQUIPMENT
ON at 78-F & OFF at 75-F that is a 3 degree differential setting;
heating equipment with TH set-point at 67 degrees F, temp drops 4-F
from the 68-F over shoot, cycles on at 64-F and turns the heating
equipment off at 68 degrees F, then
the

differential
is
4 degrees F. Some have half degree increment settings over several
degrees of differential spread. Mine has a SWING Setting of 1 to 9, I
have it set at 8 for a long
off time of two hours & one minute & a 20 minute on runtime in the
heating mode. That was the settings & on/off times on
January 25, 2012; 12:46pm noon hour; Temperature 30-F, wind chill 21-F;
The performance of my new mere 57,300-Btuh Output propane
gas
furnace.

=====================Gurgling
Pulsating Sounds at TXV:Low
evaporator heat-loads lead to reduced liquid line mass and increased
evaporator mass could be due to airflow problems. Eliminate low
evaporator heat-loads before looking into adjusting the refrigerant
charge. Gurgling and pulsation noises at the expansion device can
be
caused by low evaporator circuit heat-loads, low charge, and/or
non-condensibles and moisture in the system. Unbalanced airflow through
the various distributor circuits of the evaporator coil will cause the
TEV to close down refrigerant flow starving the coil.
Piston-flow-rators will make it impossible to properly charge the
system and cooling will be greatly compromised unless you eliminate the
cause! "Put your ear on the liquid line at the evaporator coil."On
every Rheem
condenser cover it lists "non-condensibles and or
moisture" as causes for a gurgling or pulsating noise at the expansion
device. The entire evaporator circuits, may not become active for
various reasons, - "the entire coil must become fully active for
efficient performance."

The
purpose of
these recommendations is to provide liquid refrigerant at the expansion
device and provide efficient operation. Hopefully, this will aid your
research. If I can be of additional assistance, contact me. -----------------------------------------------------------

Too
many do not properly
purge & evacuate contaminated
central air conditioning systems.

The
Triple Evacuation Method is normally done on central air
conditioning systems:

First,
remove any valve cores with a special valve core remover this
will
speed up the evacuation time. Back service valves two turns off their
back seat.

1)
Re-claim unit charge (Recover all the refrigerant)
2) Charge
system to 150 PSIG with dry nitrogen and leak test
3) On
contaminated systems replace the filter dryers. Then Repair all
leak(s)
4)
Evacuate system to 500 microns valve off & see if it holds 500
microns for ten minutes, if it holds, break
the vacuum with
dry nitrogen
5)
Evacuate system to a deeper 300 microns, valve off vac pump, &
again break the vacuum with
dry
nitrogen
6)
Evacuate system to 300 microns and charge unit (Recharge with fresh
clean refrigerant)
7) Check
to see if the Supply and Return air ducts were correctly sized &
sealed by the original installer.

Many
HVAC contractors will consider this excessive time & effort
for contaminated residential
air conditioning systems, however it is a must for low temp
applications.

The
“micron” is a metric unit of measure for
distance. The micron is a unit of linear measure; one micron equals
1/25,400ths
of an inch. Modern high capacity vacuum pumps help speed up the
evacuation process. ===================================

EFFICIENCY RATINGSAir
conditioner EER ratings, and BTUH Tons of Cooling Capacity ratings on
Air
Conditioning units are rated at an outdoor temperature of 95°F,
and an indoor 80ºF dB 67ºF WB or, a 50% Relative Humidity.

The
SEER of a system is determined by multiplying the steady state energy
efficiency
ratio (EER) measured at conditions of 82°F outdoor temperature,
80°F dB and 67°F wB indoor entering air temperature by the Part
Load Factor
(PLF) of the system. (The PLF is
supplied by
the government.)

Add to this the Part Load
Factor (PLF):
The SEER of a system is determined by multiplying the steady state
energy efficiency ratio (EER) measured at conditions of 82°F
outdoor
temperature, 80°F dB/ 67°F wb 50% RH indoor entering air
temperature by
the “Part Load Factor” (PLF) of the system.
The PLF is a measure of the cyclic performance (CD) of a system and is
calculated as follows: CD is Cyclical Data
PLF = 1.00 - (CD X's 0.5)

"The cyclic performance (CD) value
in the above equation has been determined by the
government to be 0.25." The government contends that the PLF should
equal:
[1.00 - (.25 x .5)] = .125
1.00 - .125 = 0.875, which yields: PLF of 0.875

The SEER rating is at only one
set
of conditions that are NOT typical
of what we design for. Summer Outdoor Design varies however, we usually
design for 75-F indoors NOT 80-F, also when systems' are downsized
properly to achieve long runtimes the Part Load Factor becomes far less
of a factor. Always go by the EER Rating NOT the SEER rating because as
the SEER goes higher the EER ratio to it drops. Therefore, when the
system is sized properly you have have a lot more
steady-state continuous runtime cycles & the PLF will be minimized.

Proper
system
sizing for long runtimes along
with a
computerized variable speed blower motor to keep the evaporator's heatload capacity
rating optimized, would help to achieve more of the BTUH, EER, &
SEER
Ratings of the unit!

When
selecting and installing
a new unit. First, make all the
changes
you can to reduce the heat load/heat loss, --more insulation, etc. Then
have a complete room-by-room Manual J. It
was jointly developed by the Air Conditioning Contractors of America
(ACCA)
and the Air-Conditioning and Refrigeration Institute (ARI) heat
load/loss
calculation done on the house to insure correct sizing of the unit,
then
a Manual S for selecting the correct sized A/C equipment to meet the
design
load. Then use the Manual D for correct sizing of the Main and Branch
Ducts.
Manuals S and D were established by the ACCA.
Use design outdoor conditions and daily temperature range exactly
for
your location per Manual J or ASHRAE Handbook of
Fundamentals.

Otherwise, use the data for the closest location with a similar climate.Use
standard 75°F design indoor
temperature.
Make sure
the ducts are properly insulated and that there are no
leaks. First
and foremost on older systems, "both the condenser and
evaporator
coils and the indoor blower wheel must be clean and ducts
properly
sized to achieve optimal CFM airflow levels with NO air leaks." Thermostatic
Expansion Valves (TEV/TXV) systems should be set for a minimum
9-Degrees
Superheat. Print & use the linked charts below!

Additionally,
for residential air-conditioning, "supply air diffusers" and "return
air
intakes" should be at the 8-foot ceiling level or
7-foot from the floor on side-walls where the warmest air is located,
this
is for
optimal efficient heat loading of the evaporator coil during the cooling season.
For air conditioning, both Supply and Return air grilles should never
be
at the floor level due to a
mere recycling of floor level cold air.

The greater
the temperature
difference between the Return Air (RA) and the Supply Air (SA) the more
efficiently effective will be the heat loading of the evaporator coil.
Additionally, the condensation of the latent moisture heat in the air
will
also be more effectively accomplished by utilizing a higher temperature
difference.

If
you
live
in a high humidity climate, I would go for the 13 or 14-SEER unit with
a
variable speed control system, and in any
climate
with a Thermostatic Expansion Valve (TEV/TXV) refrigerant control on
the evaporator coil. Also, a new high efficiency Variable Speed blower
motor. Have a humidistat installed --wired in parallel with the room
thermostat. (Both set-points have to be satisfied before the unit shuts
down.) You will need a low cooling coil temperature and
moderate
airflow through it, coupled with long run cycles (proper equipment BTUH
sizing)
to
get the humidity down to the 50 to 55% Comfort Zone!

What
makes things even worse is that a lot of furnace ductwork and
registers,
in older homes, were originally gravity flow systems, therefore there
are
no diffusers that throw the air up and across the rooms. Those supply
air
registers should be changed out, and then pressure drops should be kept
at a minimum throughout the duct system, which helps provide more
static pressure to the diffusers where that proper velocity &
static pressure is needed for optimal
throw
upward and across the rooms.

A/C
OWNERS:
Measuring the air temperature rise across the condenser
coils is the easiest check point to determine the total amount of
latent
and sensible BTUH of heat your air conditioner is actually removing to
the outside. You will enjoy doing it, doing it could lead to making
changes
that could considerably improve your Air Conditioning System's
performance,
thus improving your total comfort while in most cases greatly reducing
your cooling bills.

Unless
the entire air
conditioning system is engineered and
designed
so that the evaporator is absorbing its optimal designed latent and
sensible
heat load under your normal summer operating conditions, indoor near
76-F.,
with the outdoor temperature locally variable, --the air conditioner
will
simply be dropping below its BTUH rating and its Energy Efficiency
Rating
(EER) and SEER rating. The more often it operates well below its
optimal
btu/hr rating the further it will fall below its rated EER and SEER.
Along
with the -- Part Load Factor (PLF) due to
oversizing
the A/C equipment, resulting in short cycling and a dramatic drop of
its Rated SEER!

Optimize
the
entire
air conditioning system and enjoy the EER and SEER you paid for,
anything
less will result in ongoing needless operating costs to you. Without a
variable
speed indoor blower the condenser temp rise differential split will
drop
down at lower indoor heat load levels. With optimal ductwork design
coupled
with adequate blower motor Horse Power and a clean blower wheel, clean
indoor and outdoor coils, and full heat load airflow CFM through the
evaporator
coil, optimal heat absorption by the indoor evaporator coil will be
achieved
and thus discharged through the outdoor condenser coil.

"A
lot of AC systems,
with older furnace
air handlers and duct systems, are not delivering anywhere near the A/C
Unit's BTUH and SEER Ratings. This is primarily due to inadequate cubic
feet per minute (cfm) of airflow through the evaporator coil, and/or
dirty
fins/coils and blower wheels.

Typical
matched units from major manufacturers have Sensible Heat Ratios (SHR)
in the 68% to 80% range (or 32% to 20% Latent). Proper mixing of the
air
and
proper distribution to individual rooms is critical for comfort.

It is
better to use the condenser formula
below to get an estimate of the
BTUH transferred to the outdoor ambient.

Additionally,
even more
common in
northern areas of the USA, is the result of supply discharge air and
return
intake air being at the floor level where all the coldest air is merely
being recycled through the evaporator coil. It is near impossible to
fully
heat load an air conditioning evaporator when the air flow is recycling
too much of the cold supply air from the floor level. For
air conditioning,
the supply air outlets and air returns should be at, or near, the
8-foot
ceiling level.

The
later model furnaces
with bigger
horsepower blower motors and blower wheels can result in too much
airflow
through the cooling coil, the result is that some incompetent,
so-called,
technicians end-up overcharging the system, trying to get a beer can
cold
suction line. The result is greatly reduced btuh system capacity and a
deadly drop in the paid for SEER level!

When supply
discharge
air diffusers and return air registers are at the floor level airflow
must
be at a much higher level to avoid mere recirculation (recycling) of
the
cold air back through the coil. Large floor fans can help circulate and
mix the air to avoid stratification! For cooling, supply and returns at
or near the ceiling level is the most efficient design.

Solving
the
Mysteries of ESP
- External Static Pressure ESP
is the static
pressure "external to the
air handler." This
is the
reading that manufacturers' refer to in their fan performance data. The ESP is the pressure
drop
through ductwork (supply and return) only,
and does not include pressure drop through unit components - heating
coils, cooling coils, sometimes filters, & so forth.

In other words, ESP is the sum
of
the static pressure drop in straight
ductwork, and the static and dynamic pressure drops in duct fittings
(i.e. elbows, tees, transition pieces, air outlets, etc.)

"Consider that on High
efficiency
furnace there is a Condenser & an
Evaporator that adds to the Supply Air Side Static."

The Return External Static
Pressure is measured as the air enters the
return opening of the equipment, the Supply External Static Pressure is
measured just outside the supply opening. Try to find the
least-turbulent air to take the readings.

To avoid
turbulence
take the
readings 3 to 5 duct diameter inches
downstream of turbulent areas.

Bacharach
says:

Take your
measurements
on both the
Return and Supply Plenums of the furnace, as
it was shipped from the manufacturer (including the filter).

This means that
if
it was a gas or oil
fired furnace, the
measurement would NOT include the AC coil. If a heat pump is
being tested, the coil would be
included.

Drill two holes
large enough to insert the
static pressure
tip, one on the
supply side and one on the return. Pressure measurements are then
taken at
each location. The measurement on the return side will be
negative with a
positive reading on the supply but you disregard the positive/negative
and just
add the two numbers together.

Once the ESP has
been determined, look at
the fan curve for
that particular
blower and determine the CFM from that chart.

If
the air
flow is
not per
manufacturers' recommendations, it is near impossible to get the
refrigerant
charge correct.

If
you leave out
the area
up to & including the A-Coil where does that leave you? The area to
the
coil & including the coil can represent major Static Pressure
problems!

It
will pay you to find
an A/C tech
that knows his field from A to Z.
Darrell Udelhoven
-----------------

In
an oil furnace installation, a high static pressure can be
partially
due to the evaporator coil being installed too close to a big round
heat
exchanger. If you have room, a reducer transition should be stalled to
funnel the air into the aperture opening of the A coil.

Installing
the
coil on to of the furnace can cause high turbulence and back pressure,
which
combined
with inadequate, (along with floor
level intake returns) ducting coupled with long runs and other
problems
could increase the static pressure so high that your blower motor's
HP will
not move enough heat loaded room air across the heat absorbing
evaporator
coils and fins to fully heat load the outside
condenser coil.

Floor
level
supply and return air quadruples the
problem. External Static Pressure (ESP) (Pressure reading before the
E-Coil) needs to be kept within or below 0.5"
Water Column for equipment 400-cfm per ton ratings, and for efficient
operation of blower motor
HP. When the Return Negative Air Static is reduced the SA ESP will be
raised
somewhat, however, the same HP blower motor, if rated for that ESP
level, will deliver more Supply
Air.

It
is very important to check the "actual" heat transfer cooling
performance
of your AC unit. There are several approaches, but we'll keep it as
simple
as possible.

This
method for testing the capacity of a system at the condenser unit
doesn't
require air flow testing equipment. However, you need to get the
manufacturer's
blower's Cubic feet Per Minute (CFM) data on the outdoor condensing
unit's
discharge airflow. The various A/C companies and/or service companies
should
also provide the A/C owner, the condenser CFM and air temperature rise.
(The test standard rating conditions are taken at 95-F outside, 80-F
inside,
50% RH inside.)

This
test only works on wrap-around condenser coil, top air discharge
condensers'
--first, check the condenser entering air dry-bulb temp., and the
condenser
dry-bulb discharge air temp., while moving the TH around in the air
stream.
This will usually be around a 18 to 28 degree condenser temperature
split/rise.

You
also need to add the additive heat of the condenser's compressor and
fan
motor. The indoor blower motor is also a heat contributing factor, not
figured in this formula.

Older
units run a higher temperature split as they use a higher capacity
compressors
with less surface coil heat transfer area. Reading the
high-side saturation
temperature of your manifold gage could be more accurate than the use
of a thermometer for checking the discharge air tmperature.
Techs should
get the
condenser air flow data in CFM from the manufacturer's engineering
data.
All the heat discharged by the condenser air flow also includes the
latent
heat of the evaporator's absorbed condensation heat, you can determine
the total BTUH of heat discharged/exhausted by the AC condenser and
thus
determine if it is getting anywhere near its BTUH rating at your indoor
thermostat setting.

(The
below condenser
temp-splits span 1.5 to 5-ton 12-SEER units. For the
12-SEER
units, my figures get 17-F for a 1.5-ton and 23-F for a 2-ton
condenser,
1400-cfm listed for both condenser fans). This is a good performance
measure
that should be part of any maintenance check since there are no duct
variables
to contend with, the coil is easy to inspect, thermometer calibration
isn't
much of an issue (if you use the same thermometer for both in and out
air),
wet bulb temp doesn't matter as you are measuring the latent heat
removal
too, and the compressor is closely matched to the condenser (the last
can
vary some with built-up systems of course). About the only thing to
mess
you up is a slow running condenser fan (a suspect if the motor runs
real
hot) or an incorrect fan blade or blade position to the venturi of the
shroud (easy to inspect).

You
can use the high-side (SCT) Saturation Condensing Temperature
on your manifold gage's dial, minus
the outdoors-ambient Temperature; the difference gives you the
condenser
temp-rise or temp/split. There is NO excuse for not utilizing this
important
diagnostic check. Always
use an accurate volt meter and amprobe to make sure you are not
overloading
the compressor's Wattage Service Factor and check the compressor
discharge
line to see that it is under 225-F.

First,
figure the 'rated' gross capacity of the condensing unit. To determine
the "Gross BTUH Heat Ejection" of the outdoor condenser: New Data =
Let's take the
total 'Watts' from the data sheets on an 17,500-Net-BTUH Heil condenser
with a 2-ton DX evaporator coil with a TEV/TXV refrigerant control.

Take
the "listed watts" of the compressor and Condenser fan and multiply
that
wattage by the Power Factor, they used to use 0.90, then times 3.413 to
get the BTUH heat additive of the
motor,
then add the listed BTUH of the condenser to that figure, and then
divide
by the condenser's CFM. Multiply that figure by 1.08 to get the
temperature
rise.

7777/16-F indoor split
= a
mere 486-cfm | [I want 750-cfm; supply and returns at floor level!]
Also,
could be an unbalanced load on the evaporator circuits causing the TXV
to shut down the refrigerant flow, among other things.

For
the uninitiated, Delta-T is the difference between the air temperature
entering and leaving the outdoor AC condensing unit. This is a good
diagnostic
check because it measures the latent heat of condensation as well as
the
sensible heat absorbed by the vaporizing refrigerant in the indoor
evaporator
coil. I'm betting when you find out approximately how many BTUH that
the
AC system is actually transferring outside, you may be shocked by how
far
it is below its BTUH rating.

His
condenser usually has a 10 temp rise split, the evaporator appears
to be under CFM heat-loaded or, it has an unbalanced heatload on the DX
coil's
circuitry allowing liquid refrigerant in the return line causing the
TXV
sensing bulb to reduce the refrigerant flow thus reducing the DX coil's
heat absorption capacity.

The probable
cause is
"an
unbalanced
airflow/heatload
through the evaporator coil.
"I have a Thermo
Pride OL 11 oil
furnace.
Those oil furnaces have a very large round heat exchanger that goes to
near the top of the furnace, --due to a low basement ceiling the DX
coil
sets perhaps illegally close to the heat exchanger causing a few of the
coil's circuits to be under heatloaded. Since the liquid refrigerant is
not completely evaporated it will cause the outlet line that the TXV
sensor
bulb is on to be too cold and the TEV will shut-down the flow, which
greatly reduces the BTUH capacity of the DX coil and the system.
On piston refrigerant control systems, they may flood back liquid which
could damage the compressor, unless the system is way under-charged.
Thermo
Pride could install airflow turning vanes just above the heat exchanger
to funnel the air directly into the DX coil, instead of most of the
airflow
hitting the bottom of the DX's drain
pan
causing extreme turbulence
back-pressure and an
imbalanced DX
coil circuitry
heatload!

Do your own
figuring
based on this formula. Get
the Motor Power Factors (PF) of the compressor and fan motor from the
manufacturers.
(Above 0.85 factor could be close.)

The
chart split listed below is at Condenser Design conditions: Indoor
Return
Air 80-F dry bulb 67-F Wet Bulb or 50% Relative Humidity as you go up
to
99% RH the condenser split could increase by up to 6-F; down as much as
4-F at a low humidity of 55-F Wet Bulb. Do your own figuring
based on this formula. Motor BTU/hr additive = Watts X's PF x's 3.413
for
Btu/Watts additive added to rated BTUH, divided by condenser fan CFM
X's
1.08 = condenser Temp-Split. Get
the Motor Power Factors (PF) of the compressor and fan motor from the
manufacturers.
Some of the temp-split figures need
correcting,
will do ASAP. Some Splits rounded.

The
condenser fan speeds are slower on several of the 10-SEER Tonnage
Models. We are
only
trying
to get a figure to go by for a comparison. When new condensers and
Evaporator-coils
"are installed on older air handlers" or due to ductwork even
new
ones, evaporator coils are usually NOT heat-loaded to the nominal
BTUHR
design of the system. (Additionally, always check voltage and then
the amp draw!) The Base Spec sheets 12-SEER part no. 421 41 33301 03,
Feb
2001. These are the Comfortmaker® units, which are nearly identical
to Heil® units. I used the first rating on each tonnage class.
While
the "Performance Cooling Data" is listed at a 95-F outside ambient
temperature,
you can adjust the indoor airflow to get the Nominal BTUH Rating at the
customer's normal indoor stat' temp' setting and the most outside
temperature/degree
operating hours. Take the "listed watts" of the
compressor
and Condenser fan and multiply that wattage by 0.85 X's 3.413 to get
the
BTUH heat additive of the motor then add the listed BTUH of the
condenser
to it, and then divide by the condenser fan's CFM. By using the
various
units' "base specification sheet data" from the dealer, you can
determine
if it is operating near its BTUH capacity rating. Some
packaged units run a very high condenser discharge CFM airflow! Some
"Condenser Makes" will have different temp-splits. The 2-ton
10-SEER,
Janitrol; GMC; Goodman; with the U-29 E-Coil delivers less btuh, or
23000-btuh,
I subtracted a reasonable amount from the total of the wattage and come
up with 19 to 20-F temp-split. That is "if" its CFM is 1400, --get the
figures on the "different Makes." The figures are used to provide an
idea
of what the condenser temp-split should be for use by the unit's owner
and the service tech.

The
amp draw can vary from 5.7 to 10.7 amps on my Kenmore window unit's
spec
sheet. The nameplate rating is 7.5 amps at 115 volts, 10.5 that's 5
amps
X's 115 volts is 575 watts, 7.5 amps is 862.5 watts or around 33% above
the nameplate rating. [1.3 SF] It will handle up to a 120-F outside
ambient.

When I
used
a fan to increase the airflow through the evaporator coil
both
the temperature and the humidity dropped faster! This proved to
me that
low air volume may not increase the
rate of
dehumidification. Also, as the temp drops more moisture has to
be
condensed out by
the evaporator to get the same percentage of humidity reading.

Service techs, check
the
voltage at the unit and use your amp probe to see if the compressor is
within its service factor wattage rating. Check the discharge line to
see
that it is under 225-F.

The
idea is to get some condenser temperature rise split perimeter curves
with which to
gauge
its actual BTUH heat transfer performance, against your unit's Listed
BTUH Rating.
Then if the INDOOR AIRFLOW through the coil is optimal & Superheat
and Sub Cooling are within specs, the unit should
be getting its optimal BTUH and EER ratings for the existing
conditions.

The
larger your residential unit is the more apt the indoor air delivery
system
and
blower will fall short of the required air flow. In some cases, even
your
3.5 or 4-ton cooling system may only be delivering 2.5-tons of
cooling
BTUH capacity.

You
need to know somewhere near at what BTUH capacity your AC is operating
when the room temperature is where you normally have it and the outdoor
ambient is near your average cooling day temps. With a Thermostatic
Expansion
Valve refrigerant control it may not freeze up but simple shut down the
flow rate and back up liquid refrigerant in the condenser coil greatly
reducing its capacity, as well.

A
few "important qualifications" are in order here: checking the
condenser
discharge airflow temperatures will not work on units' where "the
blower
is underneath and blows the air up through a flat table top
condenser
coil because the temperature readings will vary across the entire
surface
of the condenser coil." You need to identify the liquid saturation
sub-cooling
temperature point on the coils where the "liquid should begin near the
liquid line outlet. The highside manifold gauge will indicate the
condenser
temperature. ================================For
efficiencies sake, do this immediately. Measure the Return Air
duct/chase
area. If it's a round duct measure the inside diameter, I'll give you
the
sq. ins., if square or rectangular multiple the two dimensions for sq.
in. area. The sq.in. Return Air throughput ducting area should exceed
the Supply Area ducting. For Sq.Ins.of Rd duct, i.e., An 8" round duct:
dia.
8 Xs* 8 = 64 Xs * .7854 = 50-Sq.In. On
smaller systems, take your air conditioner's btuh and divide it by
150,
(or dividing 24,000-btuh by 150 will give you 160 sq.ins., (14" Rd.
duct,)
close to a 0.05" return air duct Static Pressure drop) to get the
amount
of free air square inches for the Return Air duct system. It is
best to use the manual D. I also use an ASHRAE Air Graphed Friction
Chart, or use a Duct calculator based on the manual D.

For
a small 1.5-ton system I would go with 154 Sq. Ins. or a 14" Rd duct.

After
any duct work or other changes and before you make all the recheck
tests,
it is very important that your condenser coil and evaporator coil and
indoor
blower wheel be squeaky clean.

Also,
in older homes many times the supply and return air are both at the
floor
level rather than at the ceiling level, this colder air will tend to
reduce
the evaporator's heat load at standard CFM delivery rates, requiring an
increased CFM. However, using air temperature stratification levels in
conditioned areas with high ceilings allows the warmer air to act as an
insulating barrier at the ceiling. View my other pages on static
pressures,
CFM air flow and AC efficiency.

Additionally,
manufacturers could be helpful to the service and installation
technicians
if they would provide all the data possible with the units. The
temperature
rise across the condenser coil should be on the metal nameplate along
with
the CFM air discharge rate of the condenser.

Also,
a permanent indoor blower curve graph chart should be on the furnace or
air handler's panel. This would save valuable time and give the
technicians
vital information with which to optimize the air conditioner's
performance.

These
tests will reveal if the entire AC air handling System, ductwork,
blower,
etc., were properly sized and conditioned space loads balanced when
installed.
Later, if necessary, you can then make more refined changes to achieve
the cooling and air flow you want to each conditioned space knowing
that
you are working with the full Nominal BTUH Rated Capacity and SEER that
your AC matched System was designed to deliver.

Some
more component airflow variables are: disposable filters .05" to .30";
pleated filters .10" to .45"; Electrostatic filters .20" to .80",
transitions,
boots .05" to .35"; long air turning vaned elbows .01" to .10"; and
duct
length .05" to .20 of an inch of pressure drop. From the high end
aggregate
to the low end on all these components is a hugh pressure differential.
It doesn't take much to get above .80".

It
is good to have a little extra blower horse power and cubic feet per
minute
of air flow to do your final room delivery balancing with. Every
component
in the air delivery system can be selected within pressure drop
variables.

Here
are a couple component variables you can select from to balance the
delivery
air flow and cooling. You can buy supply air diffusers and return air
grilles
for various rooms from .02" to .15" pressure drops. Put the lower
pressure
drop registers in the rooms that need the most airflow and higher
pressure
resistance ones where you need less airflow.

You
will need a technician that knows how to diagnose the other numerous
causes
of low heat transfer. I will list only a few of them.

A
rare situation could happen "in northern states" when there is too much
air flow and a heavy heat load, --because an inexperienced so-called
tech
might keep adding refrigerant trying to get the Super Heat down and
suction
line colder -- which would overcharge the system filling too much of
both
coils with liquid refrigerant, thus greatly reducing their capacity to
absorb and then dissipate heat.

The
piston/orifice must be checked for equipment model mismatch (the charts
for orifice size are only useful when you have both the outdoor and
indoor
unit model numbers). I've found refrigerant flowrater pistons installed
backwards allowing liquid freon to bypass the tiny orifice hole, -the
results
are very interesting!

A
well informed tech knows how to use his amp probe, and pressure gages
to
trouble shoot conditions. He will evaluate the Suction pressure and
Super
Heat, Head Pressure and Liquid Subcooling, and check the indoor Static
Pressure and air flows first, --so he knows the aforementioned checks
will
provide valid readings.

A
qualified tech is able to detect all of the many things that can
destroy
your units capacity and SEER efficiency. A few are: suction or liquid
line
restrictions, plugged cap tube, or malfunctioning TXV, hot gas
discharge
restriction, unbalanced load on evaporator coil, over or under charge
of
refrigerant, inefficient compressor. Dirty coils, dirty indoor blower
wheel,
clogged air filters, high back pressure supply air diffuser grilles,
restricted
return air supply, and so forth.

If
anyone has different formulas or figures please present them to me.
I've
been retired since 1994 so am leaving it to all you techs to contact AC
companies and ask them to furnish the test information and to tap the
air
handlers so it would be easy to check static pressures ahead of the
coil
especially on oil furnaces.--------------------Determining
which metering device the system has without physically lookingIf you do not absolutely know whether the metering device is a TXV, or a fixed orifice device or cap tube.

Hook up your manifold gauges, block off considerable condenser air intake
for a short time.
If the
suction pressure starts rising, you have a piston, or a cap tube.
If only the high side goes up, you have a TXV.
Double check using Superheat, if Superheat stays relatively stable when the pressures change it's a TXV.Have things with you in your van or truck to block-off the entering condenser air
for a short time.
Check every time you are not certain what metering device it has.
There will be a lot of guessing in the future.You're
going to gasp at what I suggest will greatly improve your (3-Ton)
Return Air filtering situation, & blower efficiency...

A filter grille, with a clean
low
resistant filter in accordance with
Manual D, should stay within 300-fpm velocity.

The formula is 300-fpm X's
4.1666=
1250-CFM or 3-Ton of airflow.

The problem is that the filter
Grille & the filter, both, reduce
the free air area!

Therefore, when you figure the
area needed, they say, 2-CFM per sq.in.,
I'd use 1.25-CFM per sq.in., of the actual grille & filter area, not the outside
measurements. 1200-CFM / 1.25 = 960-sq.ins.,
or
two 400-sq.in return filter grilles.
You could even use two 500 or more sq.in., filter grille racks; sounds
far out huh, but it will work just fine.

Hart&Cooley usually just
show
the RA Grille sizing, Not the filter
grille, plus the the filter's Ak sq., open area! That always calls
for increased sizing for more Efficient Filtering & Return Airflow
Efficiency. ha...

You will never get too much RA
filter area, the more the better,
because as the filter loads the velocity will go above 500-fpm velocity
where the filter begins to allow too much debris blow-by.

Filter box depth sizing

Having a large filter/grille
area
is of little value if there is
insufficient filter box depth, so that the RA duct is way too close to
the filter/grille.

Figure two 14” duct runs, if
jammed too close to the filter, each duct
collar opening would only be 154-sq.ins., which explains why the
filter box depth is critically important to an unimpeded return
airflow.
- Udarrell

Every
manufacturer should
furnish
blower curve charts with their units and also put them on the Internet
for
service
tech's to download and print. Also, air conditioning codes should be
updated
in respect to proper sizing of the duct work which must include all the
pressure inducing factors when sizing the supply and return ducts.
Also, illustrate best furnace to evaporator coil transitions,
especially on oil furnaces! You should always keep the ESP to
0.5" or mfg'ers listing.

The
evaporator must be mounted 4 to 6
inches above this model oil furnace to achieve adequate airflow!

Also,
air conditioning codes should be updated in respect to proper sizing of
the ductwork, which must include all the pressure inducing factors when
sizing the supply and return duct systems.

We
also need the pressure drop figures on the condensers in the high
efficiency
furnaces, --that should be a data tag requirement! Knowing the operating
static pressure
is a first order essential toward accurately identifying the operating
CFM. If ductwork retrofitting doesn't solve the problem; Blower wheel
RPM
and blower motor Horse Power may need to be increased to achieve the
optimal
CFM to achieve your Unit's rated nominal BTUH and Energy Efficiency
Rating.
(80% don't). There ought to be a code
requiring
every manufacturer of an air-handler or furnace to provide capped hole taps
ahead
of the evaporator coil and ahead of the blower for easy static pressure
testing access.

Read the
pressure on
the gauge, and record the reading on the supply side, then on the
return
side. Use a (+) sign before the positive or
supply
side reading to show where it was taken, and a (-) sign before the
negative
or return side reading. Add
the two pressures. Disregard the positive and negative signs before the
pressures, because both negative and positive pressures affect the fan
as a force, so they must be added together to determine the total
resistance
the fan has to overcome. For example a +0.35" I.W.C. plus a -0.25"
I.W.C.
equals a total static pressure reading of 0.6" I.W.C.

Record
the
pressure readings on a record sticker on the furnace plenum as a
diagnostic
report for future reference and use, and on the service invoice ticket.
Any future changes in static pressure will reveal a change in the
system
that should be addressed. Our
federal government along with every state and all the Electrical
Utility
Companies ought to be supporting the testing and upgrading of all air
conditioning
systems, new and old, in order to reduce electrical demand and brown
outs. Check
the temperature rise across the outside condensing unit, get in touch
with
a good AC tech if you even have a hint your system is not operating up
to its optimal efficiency level.

Call
your local Utility Company
and
query
them about their energy saving initiatives, if they don't have any,
--request
that they develop such programs ASAP.